1. Field of the Invention
The present invention generally relates to a thermal printer, and more particularly, to a thermal printer having an improved cutting mechanism.
2. Prior Art
Printing methods carried out by a thermal printer are classified into the following two methods: serial printing method for carrying out a printing on a recording sheet while a thermal head is moving in a line printing direction and line printing method in which a fixed-type line thermal head having heating elements corresponding to all dots effects a printing on a sheet.
According to the thermal printer adopting the above conventional method, as shown in FIG. 4, a sheet 2 on which all lines of one page have been sequentially printed by a thermal head 1 is cut to a predetermined size by a cutting device 5, comprising a cutting blade 3 and a receiving blade 4, positioned forward from a printing heating element array 11 of a thermal head 1.
The cutting position 9 of the cutting device 5 is disposed at a long distance forward from the thermal head 1. When the rear end of a sheet portion 7 corresponding to a preceding page is cut, the position corresponding to the front end of a sheet portion 8 corresponding to the subsequent page is positioned at a short distance forward from the heating element array 11. Therefore, the rear end of the sheet portion 7 does not coincide with the front end of the sheet portion 8. That is, the sheet is wasted in the range from the position corresponding to the front end of the sheet portion 8 to the rear end of the sheet portion 7. For this reason, while a printing is carried out, it is necessary to make an adjustment so that the front end of the sheet portion 8 is fed to the cutting position 9 of the cutting device 5.
Time is spent while feeding the front end of the subsequent sheet portion to the cutting position and the sheet is wasted in the range described above. Further, it is necessary to provide the printer with a device which stops the front end of the subsequent sheet portion to be cut at the cutting position and in addition to the time spent for feeding the sheet, an extra cutting period of time is required.
In order to prevent the above time spent, and minimize the loss pieces of sheet unused for printing, it is necessary to position the cutting device as near as possible to the thermal head 1. Although the printer is designed to accomplish this purpose, the cutting blade 3 cannot spatially be positioned rearward of the peripheral surface of a platen roll 10, i.e., the cutting device cannot be positioned near the thermal head 1. Therefore, although the distance between the cutting device and the thermal head 1 is shortened to the greatest extent, it is necessary to provide the printer with a process for feeding the sheet approximately 15mm from the heating element array 11 of the thermal head 1 to the cutting position. This is the reason why a printing cannot be carried out at a high speed and the sheet is wasted.
In another means to minimize the waste of the sheet, it is possible to move the front end of the subsequent sheet portion backward to the heating element array after the sheet is cut, then, perform a printing.
According to this method, the wasted area of the sheet can be decreased, however, it is necessary to provide a printer capable of additionally executing a process for moving the sheet backward. Consequently, the printer is incapable of carrying out a printing at a high speed.